Electron-beam excitation laser

ABSTRACT

An electron-beam excitation laser has a laser structure with a light emitter and reflectors on one hand and an electron source on the other hand, wherein at least part of the light emitter or reflectors has a multidimensional photonic crystal structure. An electron-beam excitation laser includes an electron source emitting electrons and a laser structure consisting of a light emitter and reflectors, accelerates electrons from the electron source, and irradiates the electrons to the laser structure to emit a laser beam from the laser structure, wherein the reflectors and/or the light emitter in the laser structure are formed with multidimensional photonic crystals in which dielectrics with different dielectric constants are arrayed in a plurality of directions at periodic intervals, and one of the dielectrics with different dielectric constants may be formed with a light-emitting material.

BACKGROUNG OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an electron-beam excitationlaser, and more particularly, to an electron-beam excitation laseremitting light distributed from the visible region to the ultravioletregion. An electron-beam excitation laser according to the presentinvention can be used as a light source for a laser beam printer, anoptical recorder, optical communications, a pointer, a display, and soon.

[0003] 2. Related Background Art

[0004] A laser consists commonly of a laser medium, a resonatorincluding a reflector, and an excitation source. A laser medium obtainsenergy from an excitation source to emit light with a specificwavelength, so that a laser beam is generated in a state that allowsamplification with gain. An optical resonator reflects light emitted bythe laser medium to return it to the medium. The light is caused toreciprocate many times to be progressively amplified thereby cause laseroscillation. Lasers come in various types according to what they use asa laser medium: a gas laser which uses a He—Ne mixture, argon gas or thelike; a solid laser which uses Nd:YAG, Ti:sapphire or the like; a dyelaser which uses a dye; and a semiconductor laser which uses asemiconductor made of GaAlAs or the like. An optical excitation laserwhich uses light, a current injection laser which uses current, anelectron-beam excitation laser which uses an electron beam. Asexcitation source, such lasers are known as: a light excitation laserwhich uses light; a current injection laser which uses current; and anelectron beam excitation laser which uses electron beam. Resonatorsinclude a Fabry-Perot resonator, which uses a reflector, a prism, and adiffraction grating, and a ring resonator. Semiconductor lasers includethose which use a cleavage plane or a multilayer film as a reflectingsurface, distribution feedback (DFB) lasers, and distribution Braggreflection (DBR) lasers.

[0005] A semiconductor laser is small and light, consumes a small amountof electric power, and offers high electricity-light conversionefficiency. To provide a higher-density optical recorder and a colordisplay (refer to Japanese Patent Application Laid-Open No. 6-89075), asmall laser is hoped for which emits light with a short wavelength,especially light distributed from the blue region to the ultravioletregion. For a reason of the exposure performance of a laser beam printeralso, such a small laser is demanded. However, it is difficult to causelaser oscillation by current injection, using a wide-band-gapsemiconductor because of its electrical characteristics, such as thefact that such a semiconductor cannot freely be doped. On the otherhand, all types of direct-gap semiconductors, especially direct-gapsemiconductors which are difficult to use for current injection laserscan be used for electron-beam excitation lasers. Because of this,direct-gap semiconductors are expected to be used for laser oscillationfrom the ultraviolet region to the infrared region.

[0006] A common electron-beam excitation laser will be described below.FIG. 17 shows the structure of a conventional electron-beam excitationlaser. In the figure, a reference numeral 101 indicates a substrate;102, a light emitter (active layer); and 103 and 104, reflectors. Whenelectrons are emitted from an electron source, not shown, the lightemitter 102 is excited, and the reflectors 103 and 104 serves asresonators, so that laser oscillation occurs, thus emitting a laserbeam. In FIG. 17, a reference numeral 200 indicates a direction ofelectron emission, and a reference numeral 300 indicates a direction oflaser beam emission. Such is also the case with other figures.Semiconductors containing a group II-VI group compound, such as ZnS,CdTe, or ZnSe, are mainly used for the active layer. As a lightreflector, are used a substrate cleavage plane, a metal reflector madeof Al or the like, dielectric multilayer film made of SiO₂, TiO₂, or thelike, and multilayer reflector, that is, a combination of two compoundsemiconductors with different refractive indexes are used for thereflectors constituting a resonator.

[0007] A small electron-beam excitation laser has been reported whichwas designed using a spint type electron emitting diode and aCdTe/CdMnTe-based laser structure (Applied Physics Letters, Vol. 62, p.796, 1993).

[0008] The following problems have prevented conventional electron-beamexcitation lasers as described above from being brought into practicaluse:

[0009] (1) Conventional electron-beam excitation lasers are low in lightemission efficiency and high in oscillation threshold value. Laseroscillation occurs over a wide wavelength region in various modes.

[0010] (2) When a thick reflecting layer is provided so that its side towhich an electron beam is irradiated has sufficient light reflectingcapability, an electron beam attenuates by the time it reaches theactive layer, thus lowering light emission efficiency. To prevent such areduction in light emission efficiency, electron-beam acceleratingvoltage must be increased.

[0011] (3) Because a laser structure (a semiconductor layer) is made byvapor-phase growth methods, such as MBE and CBE, the structure iscostly, so that lasers using such a structure are difficult to offer atlow cost.

SUMMARY OF THE INVENTION

[0012] In light of the foregoing, it is an object of the presentinvention to provide a high-performance electron-beam excitation laserwhich features improved light emission efficiency, a reduced oscillationthreshold value, a narrow laser oscillation wavelength range, a reducednumber of laser oscillation modes, and the like and is easy to produceat low cost.

[0013] An electron-beam oscillation laser according to the presentinvention which has a laser structure with a light emitter andreflectors on one hand and an electron source on the other hand, whereinat least either the reflectors or light emitter has a multidimensionalphotonic structure.

[0014] Specifically, an electron-beam excitation laser according to thepresent invention which includes an electron source emitting electronsand a laser structure consisting of a light emitter and reflectors,accelerates electrons from the electron source, and irradiates theelectrons to the laser structure to emit a laser beam from the laserstructure, wherein the reflectors in the laser structure are formed withmultidimensional photonic crystals in which dielectrics with differentdielectric constants are arrayed in a plurality of directions atperiodic intervals.

[0015] An electron-beam excitation laser according to the presentinvention which includes an electron source emitting electrons and alaser structure consisting of a light emitter and reflectors,accelerates electrons from the electron source, and irradiates theelectrons to the laser structure to emit a laser beam from the laserstructure, wherein the light emitter in the laser structure is formedwith a multidimensional photonic crystal in which dielectrics withdifferent dielectric constants are arrayed in a plurality of directionsat periodic intervals, and one of the dielectrics with differentdielectric constants is formed with a light-emitting material.

[0016] An electron-beam excitation laser according to the presentinvention which includes an electron source emitting electrons and alaser structure consisting of a light emitter and reflectors,accelerates electrons from the electron source, and irradiates theelectrons to the laser structure to emit a laser beam from the laserstructure, wherein the light emitter and reflectors in the laserstructure are formed with multidimensional photonic crystals in whichdielectrics with different dielectric constants are arrayed in aplurality of directions at periodic intervals, and one of thedielectrics with different dielectric constants in the multidimensionalphotonic crystal forming the light emitter is formed with alight-emitting material.

[0017] According to the present invention, using multidimensionalphotonic crystals for reflectors in a laser structure allows lightconfinement to be effective, laser efficiency to increase, the laseroscillation wavelength range to be narrow, and the probability of laseroscillation in a single mode to increase. Especially, making part of thereflector on the side of electron-beam emission vacuum provides thereflector with both satisfactory reflection performance and a sufficientelectron-beam transmittance, thus allowing laser oscillation to occur ata low threshold value (i.e., at a low acceleration voltage).

[0018] According to the present invention, using a multidimensionalphotonic crystal for a light emitter in a laser structure allows laserefficiency to increase, the laser oscillation wavelength range to benarrow, and the probability of laser oscillation in a single mode toincrease in a mode in which photonic band group velocity is low and alocal mode accompanying defects. Using multidimensional photoniccrystals for both a light emitter and reflectors in a laser structureoffers more advantages and higher performance, compared with using amultidimensional photonic crystal for either the light emitter orreflectors. Giving a multidimensional photonic crystal an anodizedalumina nanohole structure allows an electron-beam excitation laser tobe easily made at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 shows the structure of an electron-beam excitation laser ofthe present invention;

[0020]FIG. 2 is a perspective view of the laser structure in FIG. 1;

[0021]FIG. 3 is a perspective view of another laser structure;

[0022]FIG. 4 is a perspective view of still another laser structure;

[0023]FIG. 5 is a perspective view of a further laser structure;

[0024]FIG. 6 shows a direction of laser beam emission;

[0025]FIG. 7 shows a multi-electron-beam laser;

[0026]FIGS. 8A, 8B and 8C show a laser structure whose reflector only ismade of a photonic crystal, a laser structure whose light emitters onlyare made of a photonic crystal, and a laser structure whose reflectorand light emitters are made of a photonic crystal;

[0027]FIGS. 9A, 9B and 9C show a two-dimensional photonic crystal;

[0028]FIGS. 10A, 10B and 10C show a three-dimensional photonic crystal;

[0029]FIG. 11 shows a photonic crystal containing a defect;

[0030]FIGS. 12A and 12B show a two-dimensional photonic crystal which isused for a reflector;

[0031]FIGS. 13A, 13B and 13C show two-dimensional photonic crystalswhich are used for light emitters;

[0032]FIGS. 14A, 14B and 14C show two-dimensional photonic crystalswhich are used for a reflector and light emitters;

[0033]FIG. 15 shows a two-dimensional photonic crystal made of anodizedalumina;

[0034]FIG. 16 shows an apparatus which produces two-dimensional photoniccrystals with anodized aluminum; and

[0035]FIG. 17 shows a conventional electron-beam excitation laser.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0036] Referring now to the drawings, embodiments of the presentinvention will be described in detail below. FIG. 1 shows anelectron-beam excitation laser of the present invention. In the figure,a reference numeral 1 indicates a vacuum container. An electron source 2which emits electrons is disposed at the bottom of the vacuum container1, and a laser structure 3 which produces a laser beam is disposedopposite to the electron source 2 under the top of the vacuum container1. The laser structure 3 consists of a light emitter (a light-emittinglayer) 4 and reflectors (reflecting layers) 5 and 6 which sandwich thelight emitter. The reflectors 5 and 6 serve as a resonator whichrepeatedly reflect light from the light emitter 4. Electron acceleratingmeans 7 is a power supply which applies a predetermined voltage betweenthe electron source 2 and laser structure 3 to accelerate electrons fromthe electron source 2.

[0037] Electron emission devices, such as a thermoelectron emissiondevice, an electric-field emission device, an MIM type electron emissiondevice, surface conduction type electron emission device, can be used asthe electron source 2. To reduce a laser in size, electron emissiondevices are preferably used which are small and highly efficient and canbe formed on a substrate, such as a spint type electric-field emissiondevice, an MIM type electron emission device, and a surface conductiontype electron emission device. As the electron source 2, electronemission materials which are good at emitting electrons, such as diamondand carbon nanotubes, may be disposed opposite to the laser structure ona substrate. A photoelectron emission device can be used as the electronsource 2. When a photoelectron emission device is used in such a manner,electrons emitted from the photoelectron emission device due to inputlight are accelerated using electron accelerating means and irradiatedto the laser structure, so that output light is emitted from the laserstructure. This means that an optical amplifier and a light-lightconverter are provided. The electron accelerating means can becontrolled to modulate the amplifier.

[0038] A power supply or a pulse power supply which range in voltagefrom 10 V to 100 kV can be used as the electron accelerating means 7. ADC power supply and a pulse power supply can provide continuouslaser-beam oscillation and pulsed laser-beam oscillation, respectively.An electron-beam focusing electrode can be disposed in the vacuumcontainer 1 to control the electron-beam diameter.

[0039] As described above, the laser structure 3 consists of the lightemitter 4 and reflectors 5 and 6, which serve as a resonator. In theembodiment in FIG. 1, the laser structure 3 is structured by interposingthe light emitter 4 between the reflectors 5 and 6 as shown in FIG. 2.Variations of the laser structure 3 are available. For example, thelight emitter 4 and reflectors 5 and 6 are disposed side by side, withthe emitter in between, as shown in FIG. 3; the light emitter 4 isembedded in the reflector 6 so that the reflector is in contact with thetop, bottom, and sides of the emitter 4, as shown in FIG. 4; and theentire light emitter 4 is embedded in the reflector 5, as shown in FIG.5.

[0040] When a predetermined voltage is applied to the electron source 2,using the electron accelerating means 7, electrons from the electronsource 2 are accelerated and irradiated to the laser structure 3.Irradiating electrons to the laser structure excites the light emitter 4in the structure 3 and makes the reflectors 5 and 6 serve as aresonator. Thus laser oscillation occurs, so that a laser beam isemitted. Appropriately setting the reflectance of the reflectors in eachof the laser structures in FIGS. 2 through 5 allows any of the followinglaser beam emission directions to be chosen at will: (1) the directionin parallel with the direction of electron incidence (the direction ofan arrow A), as shown in FIG. 6, (2) the direction opposite to thedirection in parallel with the direction of electron incidence (thedirection of an arrow B), and (3) the direction at right angles to thedirection of electron incidence (the direction of an arrow C).

[0041] When a plurality of electron sources 2 are disposed in the vacuumcontainer 1 as shown in FIG. 7, a plurality of laser structures 3 can bedisposed opposite to each of the plurality of electron sources.Disposing a plurality of electron sources 2 and laser structures 3 insuch a manner provides a multi-electron-beam excitation laser which emita plurality of laser beams at a time. In FIG. 7, a reference numeral 4indicates a light emitter; 5, 6, and 11, reflectors; 7, electronaccelerating means; 13, a control electrode; and 14, electron numbercontrolling means. In the following description, parts with the samefunction are provided with the same reference numeral. Applying apredetermined voltage between the electron sources 2 and the controlelectrode 13, using the electron quantity controlling means 14 allowsthe number of electrons from the electron sources 2 to be controlled.Such an arrangement can be applied to the apparatus in FIG. 1.

[0042] Material for the laser structure 3 will be described below. Anylight-emitting material which emits light distributed over theultraviolet, visible, and infrared regions may be used as a laser mediumforming the light emitter 4 in the laser structure 3. Such materialincludes a semiconductor, a fluorescent substance, dye, andlight-emitting glass. A direct-transition semiconductor can preferablybe used which is made from a group II-group VII compound such as ZnO,ZnS, or CdS; a group IIIb-group V compound such as AlAs or GaP; a groupIII-group V compound such as GaN or AlN; a chalcogenide compound, suchas MgS or MnS; or a mixed crystal of these compounds.

[0043] Available fluorescent substances include red fluorescentsubstances for CRTs, such as Zn₃(PO₄)₂:Mn²⁺; (Zn, Cd)S:Ag, YVO₄:Eu⁺³,Y₂O₃:Eu³⁺ and Y₂O₂S:Eu³⁺; green fluorescent substances such asY₃Al₅O₁₂:Tb³⁺; blue fluorescent substances, such as ZnS:Ag; and (La, Y)OBr:Ce³⁺, (La, Gd)OBr:Ce³⁺ and so forth. Fluorescent substances used forlight-emitting displays excited by an electron beam of a low voltageranging from 10 to 100 V may also be used, including ZnO:Zn, SnO₂:Eu⁺³,and Y₂O₃:Eu³⁺+In₂O₃.

[0044] The reflectors may be made of multidimensional photonic crystal,described later; a substrate cleavage plane; a metal, such as Al, Ag, orthe like; a multi layer of SiO₂ and TiO₂ or a multi layer with acombination of two compound semiconductors or the like with differentrefractive indexes. The embodiment uses a multidimensional photoniccrystal especially for the laser structure 3. Specifically, amultidimensional photonic crystal is used for the reflectors 5 and 6 inthe laser structure 3 as shown in FIG. 8A, for the light emitter 4 inthe laser structure 3 as shown in FIG. 8B, or for the reflectors 5 and 6and light emitter 4 as shown in FIG. 8C. In FIG. 8A, either of thereflectors, which sandwich the light emitter 4, may be amultidimensional photonic crystal.

[0045] The photonic crystal, which is detailed in “Photonic Crystals,”J. D. Joannnopoulous et al., Princeton University Press, 1995, pp.94-104, will be briefly described below. The photonic crystal has anartificial multidimensional periodic structure, which is formed byperiodically arranging two types or more of dielectrics with differentrefractive indexes (dielectric constants). In such a medium, periodicityof the refractive index in the order of wave length generates thephotonic bands in an analogy to the band generation theorysemiconductors in which an electron wave is Bragg-reflected so that thedispersion relation between Energy E and wave number k generates bands.A wavelength region where no light exists, that is, a photonic band gapis formed, depending on the periodic structure. To control such aphotonic band, its structural interval needs to be about the lightwavelength to a fraction of the light wavelength.

[0046] Photonic crystals are classified according to their periodicdimensional number into the following: (1) one-dimensional (1D), (2)two-dimensional (2D), and (3) three-dimensional (3D). The 1D photoniccrystal has a structure which is periodic one-dimensionally. Forexample, laminated film and the DFB structure are made of a 1D crystal.The 2D photonic crystal has a structure which is periodictwo-dimensionally (that is, in the x and y directions). For example, asshown in FIGS. 9A, 9B and 9C, the structure is formed by regularlyarraying in a first dielectric 21 cylindrical second dielectrics 22which differ in dielectric constant from the first dielectric. Thesecond dielectrics 22, which have a brachyaxis shorter than thewavelength of light emitted, are regularly and two-dimensionally arrayedin the first dielectric 21 at intervals shorter than the wavelength oflight emitted. FIG. 9A is a schematic perspective view of the structureof a 2D photonic crystal, and FIG. 9B is its plan view. The seconddielectrics 22 are arrayed squarely. As shown in FIG. 9C, the seconddielectrics 22 may be arrayed trianglerly.

[0047] The 3D photonic crystal has a structure which is periodicthree-dimensionally. For example, as shown in FIG. 10A, the 3D photoniccrystal can be provided by making the 2D photonic crystal (FIG. 9A)periodic in the z direction. To make the 2D photonic crystal periodic inthe z direction, third dielectrics 23 are provided between cylindricalsecond dielectrics. The first through third dielectrics 21 to 23 differin dielectric constant. As shown in FIG. 10B, a structure is availablewhich is formed by periodically arraying dielectric spheres 24alternately in the x and y directions to stack them in the z direction.As shown in FIG. 10C, dielectric spheres 25 can be stacked to providethe 3D photonic crystal. In FIG. 10B the dielectric rods 24 providefirst dielectrics, and air between the dielectric rods 24 providessecond dielectrics. Such is also the case with FIG. 10C.

[0048] By way of example, the multidimensional photonic crystals havebeen specifically described above. When these photonic crystals are usedfor a reflector or a light emitter in a laser structure, any materials(including air and a vacuum) can be used as dielectrics with differentdielectric constants. For example, in FIG. 9A, glass and silicon may beused as the first and second dielectrics 21 and 22, respectively, orglass and air may be used as the first and second dielectrics 21 and 22,respectively. Because making a photonic crystal mult-dimensionalincreases controllability of its band structure, thus providing anespecially effective photonic band gap, a multidimensional photoniccrystal, more specifically, a photonic crystal with a structure havingtwo dimensions or more is preferably used.

[0049] For the photonic crystal, a photonic band due to its periodicstructure increases light emission efficiency because of a reduction inthe state density of wavelength of light emitted and anisotropicdispersion. A wider photonic band gap is preferable. It is preferablethat the 2D photonic crystal be formed by regularly arraying cylindricalsecond dielectrics 22 in honeycomb formation in a first dielectric 21 sothat they are symmetrical about six directions as shown in FIG. 9C, inthat the photonic band gap is open.

[0050] Defects can be disposed in part of a photonic crystal. Forexample, as shown in FIG. 11, defects 26 with a small diameter aredisposed in some of the cylindrical second dielectrics 22 which areregularly arrayed in the first dielectrics 21. These defects cause localdisorder in the photonic crystal, so that the oscillation thresholdvalue becomes smaller, thus easily providing laser oscillation in asingle mode. The defects 26 have only to differ in diameter from thesecond dielectrics 22. Defects which are larger in diameter than thesecond dielectrics 22 may be used.

[0051]FIGS. 12A and 12B are sectional views showing a 2D photoniccrystal used for a reflector in the laser structure 3. In the figures,the two-dimensionally formed structure is drawn periodically in only onedirection, and black arrows 80 indicate directions in which thestructure is not periodic. Such is also the case with other figures.FIG. 12A shows that the direction in which the photonic crystal is notperiodic is in parallel with an electron incidence direction 200. FIG.12B shows that the direction in which the photonic crystal is notperiodic is at right angles to the electron incidence direction.Especially, when a photonic crystal is used for the reflector 6 on theside of electron incidence, its structure is desirably vacuum in part toincrease distance traveled by electrons. This provides a reflectinglayer which has both sufficient reflection performance and electron-beantransmittance, thus making laser oscillation possible at a low thresholdvalue (a low acceleration voltage). If for a part of the dielectric isused vacuum to form a photonic crystal as described above, for example,the second dielectrics 22 in the 2D photonic crystal in FIG. 9A are madevacuum. When second dielectrics in the 2D photonic crystal in FIG. 12Aare made vacuum, electrons are preferably irradiated to the crystal atright angles to the direction of its period to reduce electron energyloss and effectively excite the crystal.

[0052]FIGS. 13A to 13C are sectional views of a 2D photonic crystal usedfor the light emitter 4 in the laser structure 3. FIGS. 13A and 13B showthat the direction in which the 2D photonic crystal is not periodic isin parallel with an electron incidence direction, and FIG. 13C showsthat the direction in which the 2D photonic crystal is not periodic isat right angles to the electron incidence direction. In FIG. 13A, alight-emitting material is used for the second dielectrics 22 in FIGS.9A to 9C, and rods made of the light-emitting material are periodicallyarrayed between first dielectrics 21. In FIG. 13B, a light-emittingmaterial is used for the first dielectrics 21 in FIGS. 9A to 9C, and thesecond dielectrics 22, which are voids, are periodically arrayed. InFIG. 13C, a light-emitting material is used for second dielectrics 22 asshown in FIG. 13A, and these dielectrics are periodically arrayed.

[0053]FIGS. 14A to 14C are sectional views of 2D photonic crystals usedfor a light emitter and a reflector. In FIG. 14A, the direction in whichthe 2D photonic crystal is not periodic is in parallel with an electronincidence direction, and a light-emitting material is used for a part ofthe 2D photonic crystal for second dielectrics 22 as described usingFIG. 13A to form the light emitter 4 in the 2D photonic crystal. If thelight emitter 4 is formed on the side of a laser structure center,reflectors 11 are formed with photonic crystals on both sides of thelight emitter 4.

[0054] In FIG. 14B, the direction in which the 2D photonic crystal isnot periodic is at right angles to an electron incidence direction, anda light-emitting material is used for a part of the 2D photonic crystalas in FIG. 14A to form the light emitter 4. A photonic crystal on top ofthe light emitter 4 is a reflector 5, and a photonic crystal at thebottom of the light emitter is a reflector 6. In FIG. 14C, atwo-dimensional photonic crystal which contains periodic voids 50 isused for the reflectors 5 and 6, and a two-dimensional photonic crystalwhose light-emitting material contains periodic voids 50 is used for thelight emitter 4. The direction in which the two-dimensional photoniccrystals as the reflectors and light emitter are not periodic is inparallel with an electron incidence direction.

[0055] If a 3D photonic crystal is used for the light emitter 4 in thelaser structure 3, at least one of the first, second, and thirddielectrics 21, 22, and 23 is made of a light-emitting material in FIG.10A. In FIG. 10B, for example, all dielectric rods 24 or some of themare made of a light-emitting material. In FIG. 10C, dielectric spheres25 need to be made of a light-emitting material, or gaps between thedielectric spheres 25 need to be filled with a light-emitting material.

[0056] Thes, using photonic crystals for the reflectors, light emitter,or both of these in the laser structure 3 offers the followingadvantages:

[0057] (1) Using a photonic band gap in a multidimensional photoniccrystal for a reflector makes high-level light reflection andcontainment possible. This allows oscillation to easily occur in asingle mode within a narrow frequency range and light emissionanisotropy to be controlled using photonic-crystal multidimensionality.

[0058] (2) Periodically disposing a light-emitting material in amultidimensional photonic crystal increases light emission efficiencyand reduces the oscillation threshold value. This is reasoned asfollows. A photonic crystal allows an optical mode in which groupvelocity is low to be entered. Time of interaction between a materialsystem and a radiation field is inversely proportional to groupvelocity. Thus a group velocity reduction is used to increase theamplification factor (O Plus E, Vol. 21, p. 1533, 1999).

[0059] (3) Introducing local disorder, that is, defects into a photoniccrystal allows a mode in which light exists locally in a photonic bandgap to be entered. If a light-emitting frequency is in the photonic bandgap, spontaneous light emission and inductive light emission areprohibited because no optical mode in which light is emitted isavailable at frequencies other than frequencies in the above-describedmode. Using such a photonic crystal with defects for a light emitter ora reflector causes the above-described mode to be entered, the frequencyrange for light emission and laser oscillation to be narrowed, and timeand space coherence to be increased. This makes it easy to cause laseroscillation in a single mode at a low threshold value.

[0060] The multidimensional photonic crystal has the above-describedadvantages. However, the crystal is difficult to produce, it does notfind wide application. Because a periodic structure several hundreds ofnanometers in size needs to be formed to make a photonic crystal whichemits light in the visible region, the crystal is difficult to make. Tomake a photonic crystal, techniques are used which include electron-beamexposure, dry etching, and selective growth. However, because thesetechniques pose problems of a poor yield, high cost, and so on, aspontaneously formed regular nanostructure is preferably used.

[0061] Spontaneously formed nanostructures include an array of finespheres of polystyrene or the like, a bound of fine fibers, and anodizedalumina film. Of these, anodized alumina film is the best, becauseanodizing, a simple technique, provides a two-dimensional periodicstructure, that is, a 2D photonic crystal with a large area and a highaspect ratio. The interval can be adjusted to within a range of severaltens of nanometers to five hundred nanometers, so that a photoniccrystal can be made which emits light distributed from the visibleregion to the ultraviolet region. The anodized alumina nanohole will bedescribed below.

[0062] Anodized alumina nanoholes can be made by anodizing aluminumfilm, aluminum foil, an aluminum sheet, or the like in a certainoxidizing solution (refer to R. C. Furneaux, W. R. Rigby, & A. P.Davidson, NATURE, Vol. 337, p. 147, (1989). FIG. 15 schematically showsanodized alumina nanoholes. Anodized alumina 52, which consists mainlyof aluminum, contains many cylindrical nanoholes 53. These nanoholes 53are formed almost at right angles to the surface of a substrate. Thenanoholes 53 are almost equally spaced so that they are parallel witheach other. A reference numeral 51 indicates an aluminum sheet oraluminum film.

[0063] That is, the nanoholes 53 (which correspond to the cylindricalsecond dielectrics 22 in FIGS. 9A to 9C) are arrayed regularly inhoneycomb formation in the anodized aluminum 52 (which corresponds tothe first dielectrics 21 in FIGS. 9A to 9C). The diameter 2r of analumina nanohole, which is indicated by a reference numeral 54, rangesfrom several nanometers to hundreds of nanometers. The interval 2Rbetween the alumina nanoholes, which is indicated by a reference numeral55, ranges from several tens of nanometers to several hundreds ofnanometers. The diameter and interval can be controlled according toanodization conditions. By adjusting anodization time or the like, thethickness of the anodized alumina 52 and the depth of the nanoholes 53can be controlled to within a range of 10 to 500 μm, for example. Thediameter 2r can be increased by etching, A phosphoric acid solution orthe like can be used for etching.

[0064] Two-stage anodizing or a method which forms honeycomb-liketexture (concaves of nanohole start points) on an aluminum surface andthen anodizing the surface can be used to regularly array holes (Masuda,OPTRONICS, No. 8, p. 221, 1998). Filling anodized-alumina nanoholes withdielectrics or a light-emitting material provides a highly functional 2Dphotonic crystal. Electrodeposition is an easy and highly controllablemethod for filling nanoholes. However, film forming methods includingelectrophoresis, application, penetration, CVD, or the like can also beused for that purpose. Anodized alumina can be used to easily make a 2Dphotonic crystal as described using FIGS. 9A to 9C. Using anodizedalumina for the reflectors 5 and 6 and light emitter 4 in the laserstructure 3 as described with reference to FIGS. 12A through 14C allowsan inexpensive electron-beam excitation laser to be easily produced.

[0065] Embodiments of an electron-beam excitation laser of the presentinvention will be described in detail below. The inventor made areflector for a laser structure made from anodized alumina (2D photoniccrystal) as described with reference to FIG. 15 and tested the reflectorto evaluate it. Embodiments 1 through 6 will be described below. Inthese embodiments, the laser structure 3 has a structure shown in FIGS.12A and 12B. A CdS single crystal was used for the light emitter 4 inthe laser structure 3. The CdS single crystal was polished until it was15 μm thick and annealed in an Ar atmosphere at 550° C. for one hour.Then reflectors which consisted of 2D photonic crystals made fromanodized alumina were formed on both sides of the CdS single crystal tomake a laser structure. The embodiments 1 through 6 are six types ofreflectors which consisted of photonic crystals. An aluminum filmreflector was made as a comparative example.

[0066] A method for making a reflector using anodized alumina will bedescribed below. Aluminum film 1 μm thick is formed on a CdS singlecrystal by deposition. Any method, such as sputtering, CVD, or vacuummetallization, can be used to form such film. Before anodization,concaves are formed on the surface of the aluminum film to providenanohole start points for anodization. This operation allows nanoholesto be regularly arrayed in alumina. To make nanoholes with a high aspectratio, it is preferable that the concaves be formed in honeycombformation opposite to an array of nanoholes in anodized alumina. To formnanohole start points (concave), methods can be used, including a methodwhich emits a focused ion beam (FIB), a method which makes hollows bysuch press patterning as disclosed in Japanese Patent ApplicationLaid-Open No. 10-121292, a method which uses SPM including AFM, a methodwhich makes hollows by etching after resist patterns are formed, and thelike.

[0067] Of these methods, the method which uses a focused ion beam is thebest for the following reasons. That is, the method does not needtroublesome steps, such as resist application, electron-beam exposure,and resist removal. The method also allows nanohole start points to beformed by direct drawing at desired positions a short time andeliminates the need for a workpiece to be pressurized. Thus the methodcan be used for a workpiece which is not mechanically strong. Byemitting a focused Ga ion beam, dots of concaves were formed at 190 nmintervals in honeycomb formation. Here, Ga was used as an ion speciesfor focused ion beam processing, the acceleration voltage was 30 kV, theion beam diameter was 100 nm, and the ion current was 300 pA. A focusedion beam was irradiated to each dot for 10 msec.

[0068] The above-described alumina film was anodized to make nanoholes.FIG. 16 shows an apparatus which make anodized-alumina nanoholes. In thefigure, a reference numeral 40 indicates a thermostatic bath; 41, asample; 42, a Pt cathode (a Pt electrode); 43, an electrolyte; 44, areaction bath; 45, a power supply which applies anodization voltage; 46,an ammeter which measures anodization current. In addition, theapparatus incorporates a computer and the like to automatically controland measure the voltage and current, which are not shown in FIG. 16. Thesample 41 and cathode 42 are immersed in the electrolyte whosetemperature is kept constant in the thermostatic bath. The power supply45 applies a voltage between the sample 41 and cathode 42 to anodize thesample. The electrolyte used for anodizution is, for example, a solutionof oxalic acid, phosphoric acid, sulfuric acid, or chromic acid.

[0069] Because the interval between nanoholes, that is, the structuralinterval relates with anodization voltage as expressed by the followingequation, it is desirable that the anodization voltage be set accordingto a start point array (a structural interval).

2R=2.5×Va

[0070] 2R (nm): nanohole interval

[0071] Va (V): anodization voltage

[0072] Alumina nanohole depth can be controlled by adjusting aluminumfilm thickness or anodization time. For example, nanoholes can be madeto penetrate through the entire film thickness, or aluminum film with adesired thickness can be left. By immersing an alumina nanohole layer inan acid solution (for example, a phosphoric solution), (pore widetreatment), nanoholes can be enlarged as appropriate. In addition, bycontrolling acid concentration, treatment time, and temperature, aluminananoholes with a desired diameter can be formed. In the embodiment, analumina nanohole layer was anodized in a 0.3M phosphoric bath at 75V.The layer was also subjected to the pore wide treatment, that is,immersed in a 5 wt % phosphoric acid solution at 25° C. for 70 minutesto enlarge nanoholes until their diameter reached 150 nm.

[0073] Laser structures in Embodiments 1 through 6 will be describedbelow. In Embodiment 1, almost the entire aluminum film was convertedinto anodized alumina film to make such a laser structure that the lightemitter 4 is interposed between alumina films (2D photonic crystals) asshown in FIG. 12A. In Embodiment 2, anodization was completed whenaluminum film 100 nm thick was left. That is, the light emitter wassandwiched by aluminum films, which, in turn, were sandwiched by aluminananoholes (2D photonic crystals).

[0074] In Embodiment 3, Ag film 100 nm thick, which serves as areflecting film and antistatic film, was formed on the anodized aluminafilm in Embodiment 1. As is the case with Embodiment 2, in Embodiment 4,aluminum film on one side only was anodized to obtain anodized aluminafilm, and an electron-beam was irradiated to the film from the side ofthe anodized alumina film. As is the case with Embodiment 2, inEmbodiment 5, aluminum film on one side only was anodized to obtainanodized alumina film, and an electron-beam was irradiated to the filmfrom the side of aluminum film. In Embodiment 6, niobium film was formedon aluminum film and anodized to form anodized alumina film in whichnanoholes were made horizontally (i.e., in parallel with the filmsurface) as shown in FIG. 12B. That is, in Embodiment 6, electrons wereincident in the direction in which the 2D photonic crystal is periodic.In Comparatibe Example 1, anodization was not performed, so thataluminum film 100 nm thick was directly used as reflectors.

[0075] The thus produced laser structures in Embodiments 1 through 6were evaluated using a laser structure in Comparative Example 1. Theselaser structures which use a light emitter consisting of a CdS singlecrystal and reflectors consisting of 2D photonic crystals were placed ina vacuumizer, and vacuumization was performed until a pressure of 10⁻⁶Pa was reached. Next, the laser structures were cooled to a liquidnitrogen temperature, and electrons emitted from an opposite electrongun made of LaB₆ were accelerated to an acceleration voltage of 10 to 50keV and irradiated to the structures. As a result, green light with awavelength around 520 nm was obtained by laser oscillation.Specifically, the laser oscillation threshold value was 15 to 20 A/cm²for the laser structure in Embodiment 1. On the other hand, the valuewas 20 to 50 A/cm² for the laser structure in Comparative Example 1.

[0076] Embodiments 2 and 3 needed a little higher acceleration voltagethan Embodiment 1. However, Embodiment 1 allowed oscillation bylow-current excitation, so that oscillation was highly stable over time.Although the laser oscillation wavelength range was a little wider inEmbodiment 4, compared with Embodiment 2 Embodiment 4 allowedoscillation at a low oscillation threshold value. In Embodiment 5, theoscillation threshold value was high as in Comparative Example 1.However, in Embodiment 5, the laser oscillation wavelength range wasslightly narrower than in Comparative Example 1. For the laser structurein Embodiment 6, the laser oscillation threshold value was low, at 10 to15 A/cm². In Embodiments 1, 2, 3, and 6, especially Embodiment 6, thelaser oscillation wavelength range was narrow, and a reduced number oflaser oscillation modes were available. The results obtained fromEmbodiments 1 through 6 show that using a 2D photonic crystal made fromanodized alumina for a reflector in a laser structure reduces laseroscillation threshold current.

[0077] By filling nanoholes in anodized alumina film (a 2D photoniccrystal) with a light-emitting material, four types of laser structurewith a light emitter was made to evaluate them. The structures, whichare as shown in FIGS. 13A and 14A, correspond to Embodiments 7 through10. Anodized alumina film whose nanoholes were filled with ZnO, that is,a photonic alumina crystal in which ZnO rods were arrayedtwo-dimensionally was used for the light emitter 4.

[0078] Specifically, Nb film 100 nm thick was formed on a quartzsubstrate, then aluminum film 1 μm thick was formed on the Nb film by DCsputtering. Next, as is the case with Embodiment 1, the aluminum filmwas anodized to make alumina nanoholes. These nanoholes were formed at140 nm intervals in honeycomb formation. Then the aluminum film wasanodized at 56 V, using a 0.3M phosphoric acid bath. Finally, the filmwas subjected to pore wide treatment, that is, immersed in a 5 wt %phosphoric acid solution at 25° C. for 50 minutes to enlarge nanoholesuntil their diameter reached about 110 nm.

[0079] By electrodeposition, the nanoholes were filled with ZnO to makea light emitter. The substrate was immersed in a 0.1M zinc nitratesolution at 60° C. together with an opposite Pt electrode. Next, avoltage of about −5 V was applied to the substrate to form ZnO crystalsIn the nanoholes. In Embodiment 7, ZnO crystals were let to grow untilthey protruded from the nanoholes, and then the substrate surface waspolished. In Embodiment 8, ZnO was deposited in the nanoholes until ananohole depth of about 300 nm was reached (Embodiments 7 and 8correspond to the laser structure in FIG. 13A). The substrate washeat-treated in a He atmosphere at 400° C. for one hour and overlaidwith Ag film 100 nm thick by vapor deposition to make a light emitter.

[0080] In Embodiment 9 (corresponding to FIG. 14A), Nb film strips 5 μmwide were made, then aluminum film was formed over these strips andanodized to fill nanoholes with ZnO. ZnO was deposited on those parts ofthe aluminum film having an underlying Nb film (5 μm wide) were present.That is, some of the nanoholes in the anodized alumina film (the 2Dphotonic crystal) were filled with the light-emitting material. InEmbodiment 10, a beam of more ions were locally irradiated to thesubstrate during anodized alumina production to form shallow startpoints. As a result, anodized alumina nanoholes which locally had asmaller diameter were formed as shown in FIG. 11 (the structure in FIG.13A was provided with defects in embodiment 10).

[0081] The thus produced laser structures in Embodiments 7 through 10were placed in a vacuumizer, and vacuumization was performed until apressure of 10⁻⁶ Pa was reached. Next, the laser structures were cooledto a liquid nitrogen temperature, and electrons were emitted from anopposite electron gun made of LaB₆ to irradiate a beam of electronsaccelerated to an acceleration voltage of 10 to 50 keV to thestructures. As a result, laser oscillation could be caused near aultraviolet wavelength of 390 nm. The laser oscillation threshold valuewas 15 to 20 A/cm² for the laser structures. On the other hand, thevalue was 20 to 50 A/cm² for a laser structure in Comparative Example 2,which was formed by depositing ZnO and Ag on Nb film.

[0082] As described above, the results show that using a 2D photoniccrystal made from anodized alumina for a reflector in a laser structurereduces laser oscillation threshold current. In Embodiments 7 through10, especially Embodiments 8 and 9, the laser oscillation wavelengthrange was narrow, and a reduced number of laser oscillation modes wereavailable. In Embodiment 10, a mode due to defects was found. InEmbodiments 7 through 10, introducing a light emitter into a photoniccrystal probably caused the oscillation threshold value to decrease withdecreasing group velocity.

[0083] In Embodiment 8, parts which contained almina nanoholes about 700nm high unfilled with ZnO possibly served as photonic crystals(reflectors). In Embodiment 9, that anodize alumina film on the sides ofthe light emitter consisting of a photonic crystal whose nanoholes werenot filled probably served as a reflector in the photonic crystal toeffectively contain light. In Embodiment 10, defects in the 2D photoniccrystal (anodized alumina film) may have contributed to laseroscillation.

[0084] In Embodiment 11, a laser structure which uses a GRINSH (gradedindex separate confinement) type ZnCdSe/ZnSe heterostructure produced byMBE for a light emitter was made and evaluated. The laser structurecorresponds to FIG. 12A. The light emitter has a heterostructure. Theheterostructure consists of a 1 μm thick ZnSe buffer layer on an InGaAs(100) substrate and a quantum well which is made fromZn_(0.75)Cd_(0.25)Se interposed between refractive-index change layersof Zn1-xCdxSe (x=0 to 0.05) and is disposed on top of the buffer layer.The refractive-index change layer is 500 nm thick.

[0085] A reflector made from anodized alumina was formed on theheterostructure in the same was as in Embodiment 2 to make the laserstructure. In the embodiment, start points were arrayed at 170-nmintervals in honeycomb formation, and anodization was performed at 68 Vin a 0.3M phosphoric acid bath. Finally, the laser structure wassubjected to pore wide treatment, that is, immersed in a 5 wt %phosphoric acid solution at 25° C. for 70 minutes to enlarge nanoholesuntil their diameter reached about 140 nm.

[0086] A spint type electron source was provided which has 10⁴ to 10⁵ Mochips per square millimeter. The thus produced laser structure wasplaced opposite to the spint type electron source in a glass container.After the container was evacuated, it was hermetically sealed. Aselectron accelerating means, a high-voltage power supply was connectedto the electron source and laser structure. When a beam of electronsaccelerated to an acceleration voltage of 10 to 50 keV was irradiated tothe structure, blue light with a wavelength around 480 nm was obtainedby laser oscillation. For the embodiment, the laser oscillationthreshold value was 0.3 to 0.5 mA/cm². On the other hand, for acomparative example where no anodized alumina film was disposed, thevalue was 0.5 to 1 mA/cm². The laser oscillation wavelength range wasfound to be narrow, and a reduced number of laser oscillation modes werefound to be available.

[0087] In Embodiment 12, by electron-beam lithography, a wafer with anInGaAsP/InP multiplex quantum well active layer was given a 2D photoniccrystal structure to make a laser structure. The laser structure wasevaluated. It is as shown in FIG. 14C. A wafer was provided by letting a200 nm thick InGaAs etching stop layer, a 100 nm thick InP layer, an SCH(separate confinement heterostructure) multiplex quantum well activelayer, and 100 nm thick InP layer 15 grow on an InP substrate. Theactive layer consists of an SCH layer 50 nm thick which is made fromInGaAsP (band gap energy wavelength λg=1.1 μm), an InGaAsP well 7 nmthick (λg=1.36 μm), and an InGaAsP barrier layer 15 nm thick (λg=1.1μm).

[0088] SiO₂ film was formed on the wafer, and photoresist was applied tothe wafer to form such a resist mask that circular openings 250 nm inradius are arrayed at 460-nm intervals in hexagonal lattice formation.Using the resist mask, the circular-opening pattern was transferred ontoSiO₂ film by reactive ion etching. Using the SiO₂ mask, two-dimensionalhole rows were formed on the wafer. Finally, the SiO₂ mask was removedto make a laser structure.

[0089] An electron source was made by forming nitrogen-doped diamondfilm on a silicone substrate by hot-filament CVD under the followingconditions: (1) tungsten filament temperature=2300° C., (2) substratetemperature=800° C., (3) reaction pressure=100 torr, and (4) ratio ofreactive gas to hydrogen=0.6%. The reactive gas was provided bysaturating methanol with (NH₂)₂CO, diluting the saturated solution tentimes with acetone, and vaporizing the dilution.

[0090] In this way, a laser structure was made whose light emitter andreflectors consist of 2D photonic crystals, with the emitter interposedvertically between the reflectors. In a vaccumizer, the laser structurewas placed opposite to the electron source with a 2 mm separation inbetween. When electrons were emitted from the electron source toirradiate a beam of electrons accelerated to an acceleration voltage of10 to 50 keV to the structure, laser oscillation could be caused near awavelength of 1.3 μm. The laser oscillation threshold value was 0.2 to0.5 mA/cm². On the other hand, the value was 0.5 to 0.8 mA/cm² for acomparative example in which no two-dimensional rows were provided. Theembodiment shows that using a laser structure whose reflectors consistof 2D photonic crystals reduces the oscillation threshold value. For theembodiment, the laser oscillation wavelength range was found to benarrow, and a reduced number of laser oscillation modes were found to beavailable.

[0091] In Embodiment 13, a laser structure whose reflectors consist of3D photonic crystals of dielectric spheres was made and evaluated. The3D photonic crystal in FIG. 10C, metal reflecting film, and ZnO filmwere used for the reflector 6, reflector 5, and light emitter 4,respectively. ZnO film was formed on a sapphire (0001) substrate bylaser MBE to make the ZnO light emitter. To form the film, a KrF excimerlaser beam was irradiated to a ZnO sintered target at an oxygen partialpressure of 1×10⁻⁶ torr and a substrate temperature of 550° C. toevaporate ZnO. The resulting film was about 60 nm thick.

[0092] Drops of a water solution (4 wt %) in which particles 170 nm indiameter (standard deviation of 3%) made from polystyrene were dispersedwere let to fall to evaporate water. As a result a reflector was formedin which, polystyrene particles structured themselvesthree-dimensionally and arranged. Ag film 100 nm thick was formed asantistatic and reflecting film on the face of the substrate. Ag film 200nm thick was formed as reflecting film on the back of the substrate.

[0093] In this way, a laser structure was made which has reflectorsconsisting of such 3D photonic crystals that dielectric spheres arearrayed on top of a ZnO light emitter. The laser structure was placed ina vacuumizer. When electrons were emitted from an LaB₆ electron gunopposite to the laser structure to irradiate a beam of electronsaccelerated to an acceleration voltage of 10 to 50 keV to the structure,ultraviolet light with a wavelength near 390 nm could be caused by laseroscillation. The laser oscillation threshold value was 0.1 to 0.4 A/cm².On the other hand, the value was 0.5 to 1 A/cm² for Comparative Example3 in which no polystyrene particles were disposed. The embodiment showsthat using a laser structure whose reflectors consist of 3D photoniccrystals formed with arrayed polystyrene particles reduces theoscillation threshold value. For the embodiment, the laser oscillationwavelength range was found to be narrow, and a reduced number of laseroscillation modes were found to be available.

[0094] In Embodiment 14, a laser structure was made whose light emitterhas a 3D photonic crystal structure and subjected to evaluation test.The light emitter 4 has a structure as shown in FIG. 10C. The structureis formed by placing (CdS) illuminants between dielectric spheres 25.Metal reflecting film is used for the reflectors 5 and 6. Specifically,the following process was repeated to make such a 3D photonic crystalstructure that illuminants are placed between dielectric spheres 25. Asis the case with Embodiment 13, particles 380 nm in diameter made frompolystyrene are dispersed and arrayed on a quartz substrate. Then thesubstrate is first immersed in a 0.025M CdSO₄ solution and then in anS═C (NH₂)₂ solution. This operation is repeated. During operation, bothsolutions are kept at 60° C. Ammonia is dissolved as a catalyst in bothsolutions. Ag reflecting film 100 nm thick was formed on the face andback of the substrate.

[0095] In this way, a laser structure was made whose light emitter hassuch a 3D photonic crystal structure that illuminants are placed betweendielectric spheres 25. The laser structure was place in a vacuumizer.When electrons were emitted from an LaB₆ electron gun opposite to thelaser structure to irradiate a beam of electrons accelerated to anacceleration voltage of 30 to 80 keV to the structure, green light witha wavelength near 520 nm could be caused by laser oscillation. For theembodiment, the laser oscillation threshold value was lower, comparedwith Comparative Example 4 where no polystyrene particles were disposed.That is, in the embodiment, using the laser structure whose lightemitter has such a 3D photonic crystal structure that illuminants areplaced between dielectric spheres reduced threshold current density andthe number of laser oscillation modes and narrowed the laser oscillationwavelength range.

[0096] As described above, the present invention has the followingadvantages:

[0097] (1) Using a laser structure with reflectors consisting ofmultidimensional photonic crystals improves resonator performance andlaser emission efficiency. Using such a laser structure also narrows thelaser oscillation wavelength range and provides an electron-beamexcitation laser which operates in a reduced number of laser oscillationmodes. Especially, making some of the dielectrics constituting aphotonic crystal vacuum causes the substantial intensity of an electronbeam reaching the light emitter to increase. Thus the laser oscillationthreshold current density and threshold voltage can be reduced.

[0098] (2) Using a multidimensional photonic crystal for a light emitterin a laser structure provides an electron-beam excitation laser whichfeatures increased laser emission efficiency, a narrow laser oscillationwavelength range, and a reduced number of laser oscillation modesavailable.

[0099] (3) Using multidimensional photonic crystals for reflectors and alight emitter in a laser structure provides higher performance, comparedwith using a multidimensional photonic crystal for either the reflectorsor light emitter.

[0100] (4) Making a multidimensional photonic crystal from anodizedalumina allows an electron-beam excitation laser to be easily producedat low cost.

What is claimed is:
 1. An electron-beam excitation laser which has alaser structure with a light emitter and reflectors on one hand and anelectron source on the other hand, wherein at least part of the lightemitter or reflectors has a multidimensional photonic crystal structure.2. An electron-beam excitation laser which includes an electron sourceemitting electrons and a laser structure consisting of a light emitterand reflectors, accelerates electrons from the electron source, andirradiates the electrons to the laser structure to emit a laser beamfrom the laser structure, wherein the reflectors in the laser structureare formed with multidimensional photonic crystals in which dielectricswith different dielectric constants are arrayed in a plurality ofdirections at periodic intervals.
 3. The electron-beam excitation laseraccording to claim 2 , wherein one of the dielectrics with differentdielectic constants in the multidimensional photonic crystal is vacuum.4. The electron-beam excitation laser according to claim 2 , whereinsaid multidimensional photonic crystal is formed by regularly andtwo-dimensionally arraying in a first dielectric cylindrical seconddielectrics with a brachyaxis shorter than the wavelength of lightemitted at intervals shorter than the wavelength of light emitted. 5.The electron-beam excitation laser according to claim 2 , wherein a partof said multidimensional photonic crystal has defects.
 6. Theelectron-beam excitation laser according to claim 5 , wherein saiddefects are dielectrics which differ in size from other dielectrics. 7.The electron-beam excitation laser according to claim 2 , wherein saidmultidimensional photonic crystal, which is formed by anodizingaluminum, has such an anodized alumina nanohole structure thatcylindrical nanoholes are regularly and two-dimensionally arrayed in analumina layer.
 8. An electron-beam excitation laser which includes anelectron source emitting electrons and a laser structure consisting of alight emitter and reflectors, accelerates electrons from the electronsource, and irradiates the electrons to the laser structure to emit alaser beam from the laser structure, wherein the light emitter in thelaser structure is formed with a multidimensional photonic crystal inwhich dielectrics with different dielectric constants are arrayed in aplurality of directions at periodic intervals, and one of thedielectrics with different dielectric constants is formed with alight-emitting material.
 9. The electron-beam excitation laser accordingto claim 8 , wherein said multidimensional photonic crystal is formed byregularly and two-dimensionally arraying in a first dielectriccylindrical second dielectrics with a brachyaxis shorter than thewavelength of light emitted at intervals shorter than the wavelength oflight emitted.
 10. The electron-beam excitation laser according to claim9 , wherein said second dielectrics are formed with a light-emittingmaterial.
 11. The electron-beam excitation laser according to claim 10 ,wherein said light-emitting material is made of a II-VI semiconductor orzinc oxide.
 12. The electron-beam excitation laser according to claim 9, wherein said first dielectric is made of a light-emitting material,and said second dielectrics arrayed are voids.
 13. The electron-beamexcitation laser according to claim 12 , wherein said light-emittingmaterial is made of a II-VI semiconductor or zinc oxide.
 14. Theelectron-beam excitation laser according to claim 8 , wherein a part ofthe multidimensional photonic crystal has defects.
 15. The electron-beamexcitation laser according to claim 14 , wherein said defects aredielectrics which differ in size from other dielectrics.
 16. Theelectron-beam excitation laser according to claim 8 , wherein saidmultidimensional photonic crystal, which is formed by anodizingaluminum, has such an anodized alumina nanohole structure thatcylindrical nanoholes are regularly and two-dimensionally arrayed in analumina layer.
 17. The electron-beam excitation laser according to claim8 , wherein said light-emitting material is made of a II-VIsemiconductor or zinc oxide.
 18. An electron-beam excitation laser whichincludes an electron source emitting electrons and a laser structureconsisting of a light emitter and reflectors, accelerates electrons fromthe electron source, and irradiates the electrons to the laser structureto emit a laser beam from the laser structure, wherein the light emitterand reflectors in the laser structure are formed with multidimensionalphotonic crystals in which dielectrics with different dielectricconstants are arrayed in a plurality of directions at periodicintervals, and one of the dielectrics with different dielectricconstants in the multidimensional photonic crystal forming the lightemitter is formed with a light-emitting material.
 19. The electron-beamexcitation laser according to claim 18 , wherein one of the dielectricswith different dielectric constants forming said light reflector in themultidimensional photonic crystal is vacuum.
 20. The electron-beamexcitation laser according to claim 18 , wherein said multidimensionalphotonic crystal is formed by regularly and two-dimensionally arrayingin a first dielectric cylindrical second dielectrics with a brachyaxisshorter than the wavelength of light emitted at intervals shorter thanthe wavelength of light emitted.
 21. The electron-beam excitation laseraccording to claim 20 , wherein said second dielectrics in themultidimensional photonic crystal forming the light emitter is made of alight-emitting material.
 22. The electron-beam excitation laseraccording to claim 21 , wherein said light-emitting material is made ofa II-VI semiconductor or zinc oxide.
 23. The electron-beam excitationlaser according to claim 20 , wherein said first dielectric in themultidimensional photonic crystal forming the light emitter is made of alight-emitting material, and said second dielectrics arrayed are voids.24. The electron-beam excitation laser according to claim 23 , whereinsaid light-emitting material is made of a II-VI semiconductor or zincoxide.
 25. The electron-beam excitation laser according to claim 18 ,wherein a part of the multidimensional photonic crystal has defects. 26.The electron-beam excitation laser according to claim 25 , wherein saiddefects are dielectrics which differ in size from other dielectrics. 27.The electron-beam excitation laser according to claim 18 , wherein saidmultidimensional photonic crystal, which is formed by anodizingaluminum, has such an anodized alumina nanohole structure thatcylindrical nanoholes are regularly and two-dimensionally arrayed in analumina layer.
 28. The electron-beam excitation laser according to claim18 , wherein said second dielectrics in the multidimensional photoniccrystal forming the light emitter is made of a light-emitting material.29. The electron-beam excitation laser according to claim 18 , whereinsaid first dielectric in the multidimensional photonic crystal formingthe light emitter is made of a light-emitting material, and said seconddielectrics arrayed are voids.
 30. The electron-beam excitation laseraccording to claim 18 , wherein said light-emitting material is made ofa II-VI semiconductor or zinc oxide.
 31. The electron-beam excitationlaser according to claim 28 , wherein said light-emitting material ismade of a II-VI semiconductor or zinc oxide.
 32. The electron-beamexcitation laser according to claim 29 , wherein said light-emittingmaterial is made of a II-VI semiconductor or zinc oxide.